In order to correspond to what is called a carrier aggregation that corresponds to a plurality of frequency bands and sends signals by using the a plurality of frequency bands simultaneously, a communication device in which a broadband coupler, a diplexer and a multiband switch (SW) are mounted between an antenna and a duplexer has been used.
In such a communication device, in order to keep the power of the output signal of the antenna to a predetermined value, a portion of the output signal is branched by a coupler and is detected, then the output of the amplifier is controlled based on the detection result.